The purpose of this study is to explorethe brain excitability in patients undergoing heart valve replacement surgery with cardiopulmonary bypass and the correlation with postoperative delirium

Delirium is the most common surgical patients postoperative complications of brain dysfunction. Delirium is a kind of consciousness attention and cognitive function changes of acute brain dysfunction, with volatility and reversibility of postoperative delirium (POD), increased hospital costs and length of hospital stay and mortality rate, and can lower the quality of life, lead to long-term postoperative cognitive dysfunction and dementia. The incidence of postoperative cognitive dysfunction in patients undergoing cardiac valve replacement under cardiopulmonary bypass (CPB) can be as high as 44-53%. However, since the specific mechanism of POD is still not clear, there is still a lack of effective prevention and treatment measures. Therefore, early detection and identification are helpful for the early treatment of POD.When brain injury occurs, the levels of excitatory neurotransmitters (glutamate and aspartate) will rise in a short period of time, and the high concentration of glutamate causes excessive intracellular calcium flow, causing cellular calcium overload, and generating excitatory cytotoxic effects. And abnormal electroencephalogram (EEG) is a kind of due to brain excitability/inhibitory amino acid imbalance caused by brain excitability increased result in abnormal discharge mode, can affect cognitive awareness and activities. Increased brain excitability is harmful to the potential, should avoid to happen. At present, the relationship between brain excitability and POD is still in exploring. Therefore, it is important to clarify the correlation between brain excitability and POD in patients undergoing cardiac valve replacement under CPB for improving the pathogenesis of POD.

Inclusion Criteria:

1. ASA Ⅱ - Ⅲ;
2. No cognitive impairment was assessed one day before surgery;
3. Patients undergoing elective heart valve replacement under CPB and signed informed consent.

Exclusion Criteria:

1. Non-CPB surgery, macrovascular surgery, heart transplantation, correction of congenital heart disease;
2. Stroke, schizophrenia, depression, Parkinson's disease, epilepsy or dementia;
3. Inability to communicate with language impairment or major hearing or visual impairment;
4. Liver function child-pugh Grade C, severe liver dysfunction;
5. Severe renal insufficiency requires preoperative renal replacement therapy;
6. A past history of intraoperative knowledge.

The patients undergoing heart valve replacement surgery with cardiopulmonary bypass